1. Field of the Invention
The present invention relates to a terminal slowdown apparatus for slowing and stopping an elevator car to land the car at a terminal floor.
2. Description of the Prior Art
A speed feedback control system for controlling the speed of an elevator car depending upon a speed command signal has been employed to slowdown the car with a secure feeling to passengers and to land the car precisely at the predetermined floor. It has been considered to use a computer for this purpose.
Referring to FIGS. 1 to 3, the system is briefly illustrated, through the system is further described in detail.
In FIGS. 1 to 3, the reference (1) designates a top floor; (2) designates a cam placed in a hoist way at each point departed for a predetermined distance L.sub.0 from each floor; (3A)-(3D) respectively designate the first-fourth terminal floor detectors which are switches vertically placed at points departed for each distance L.sub.1 -L.sub.4 (L.sub.0 &gt;L.sub.1 &gt;L.sub.2 &gt;L.sub.3 &gt;L.sub.4) from the top floor (1); (4) designates the car of the elevator; (5) designates a slowdown starting point detector which is a switch which contacts with the cam (2) placed on the car (4); (6) designates a cam placed on the car (4) to contact with the terminal floor detectors (3A)-(3D); (7) designates a counterweight; (8) designates a main rope which connects the car (4) to the counterweight (7); (9) designates a traction sheave of a traction machine for winding the main rope (8); (10) designates a traction motor for driving the sheave (9); (11) designates a pulse generator which is connected to the motor to generate pulses in proportion to the revolution speed of the motor (10); (12) designates a pulse counter which counts pulses corresponding to the travel distance of the car (4) from the output of the pulse generator (11) to generate car position signals (12a); (13) designates a call detection signal for detecting calls at the floors; (14) designates a digital processor; (15) designates a D/A converter which converts the digital signal from the processor (14) into an analog signal to generate a normal slowdown command signal Vn; (16) designates a digital processor which is separated from the digital processor (14); (17) designates a D/A converter which converts the digital output signal from the processor (16) into an analog signal to generate a terminal slowdown command signal Vs and which comprises D flip-flops (17a), (17b), (17c) and a D/A converter (17d) as shown in FIG. 14, the D/A converter (17) acting to write digitized pattern data from the CPU (16B) of the digital processor (14) in the D flip-flops so as to perform a D/A conversion into analog data. The polarity of the pattern is controlled by the SIGN of the D/A converter (17d); (18) designates a comparator circuit which selects the normal slowdown command signal Vn when Vn&lt;Vs and the terminal slowdown command signal Vs when Vn.gtoreq.Vs; (19) designates a speed control device for controlling the motor (10); and (20) designates a down counter for subtracting pulses of the pulse generator (11), the down counter including converters (20a) (20b) and a tri-state gate (20c) as shown in FIG. 15.
A predetermined output is given when the car (4) reaches a point departed by the predetermined distance L.sub.0 from the calling floor (hereinafter referred to as a stop floor) upon contact of the cam (2) with the slowdown starting point detector (5). The digital processor (14) calculates a distance from the present position of the car (4) to the stop floor (1) (hereinafter referred to as a residual distance) based on the output of detector (5), the car position signal (12a) and the calling detection signal (13). The data corresponding to the residual distance is read out from the slowdown command data memorized in a memory device within processor (16). The data is converted into analog data by the D/A converter (15) to output it as the normal slowdown command signal Vn and to input it into the speed control device (19) whereby the speed of the motor (10) is controlled and the car (4) is slowed down to land at the stop floor (1). This operation is performed for the terminal floors and other floors in the same manner.
On the other hand, when the car (4) approaches the terminal floor such as the top floor (1) and contacts the cam (6) with the terminal detector (3A), the detector (3A) is actuated and the digital processor (16) processes the residual distance L.sub.1 from the present position of the car (4) to the top floor (1). In the same manner for the normal slowdown command, the data corresponding to the residual distance is read out from the slowdown command data memorized in a memory device within processor (14) to output the terminal slowdown command signal Vs from the D/A converter (17).
FIG. 2 shows the relation of the normal slowdown command signal Vn and the terminal slowdown signal Vs. In the normal state, Vn&lt;Vs is given. The traction motor (10) is controlled during slowdown by the normal slowdown command signal Vn. If Vn.gtoreq.Vs is given due to a certain fault in the pulse counter (12) or the slowdown starting point detector (5), the terminal slowdown command Vs is generated from the compartor circuit (18) to land the car (4) safely at the top floor (1) in a slowdown mode.
FIG. 3 shows the relation of the terminal slowdown command signal Vs and the terminal detectors (3A)-(3C). The positions of the terminal detectors (3A)-(3C) are decided as follows (the terminal detector (3D) not being shown):
(1) the first terminal detector (3A) is placed at the point P.sub.1 slightly higher than the normal slowdown position P.sub.0 in the rated speed running (the position departed for the residual distance L.sub.0);
(2) the second terminal detector (3B) is placed at the point P.sub.2 wherein the true speed Va.sub.1 of the car (4) in the start from the position P.sub.1 at an acceleration a is equal to the terminal slowdown command signal Vs;
(3) the third terminal detector (3C) is placed at the position P.sub.3 wherein the true speed Va.sub.2 of the car (4) in the start from the position P.sub.2 at an acceleration a is equal to the terminal slowdown command signal Vs; and
(4) the ith terminal detector is placed at the position P.sub.i wherein the true speed of the car in the start from the position P.sub.i-1 at an acceleration is equal to the terminal slowdown command signal Vs.
The terminal detectors (3A)-(3D) are placed in the same manner to the positions before the place wherein the distance from the position Pi to the top floor (1) is less than 1/2 of the minimum floor distance allowed at the rated speed. In this designation, the cam (6) contacts with the terminal detectors (3B)-(3D) without increasing the true speed of the car (4) over the terminal slowdown command signal Vs even though the car (4) starts from the position P.sub.1 or higher. Thus, the terminal slowdown command signal Vs is operated whereby the car (4) safely land at the top floor (1).
The acceleration a is determined to be the maximum acceleration of the car (4) in the case of the start of the car at the saturation fault for generating the largest, normal speed command signal Vn. The maximum acceleration is determined by the limit of the traction of the traction machine and is usually 2.0 m/S.sup.2. In the case of deceleration of the terminal slowdown command signal Vs of 0.9 m/S.sup.2 and the rated speed of 240 m/min, 8 of the terminal detectors (3A)-(3i) are needed. That is, many terminal detectors are needed whereby the arrangements and control are not easy and the devices are expensive.